Swash plate type variable displacement compressor

ABSTRACT

A housing has a peripheral wall that surrounds a crank chamber. The peripheral wall has a valve chamber that is recessed radially inward from an outer surface of the peripheral wall with respect to the axis. A bimetal member, which deforms in correspondence with the temperature in the crank chamber, is arranged in the valve chamber. A valve body, which is supported by the bimetal member, is arranged in the valve chamber. The peripheral wall has a first oil discharge passage and allows communication between the crank chamber and the valve chamber, and a second oil discharge passage through which the valve chamber and a suction chamber communicate with each other. When the temperature in the crank chamber exceeds a predetermined value and deforms the bimetal member to move the valve body, communication between the first and second oil discharge passage is permitted through the valve chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a swash plate type variable displacement compressor.

Japanese Laid-Open Patent Publication No. 2007-9720 discloses a conventional swash plate type variable displacement compressor. The compressor has a housing configured by a front housing member, a cylinder block, and a rear housing member. The housing includes a plurality of cylinder bores, a suction chamber, a discharge chamber, and a crank chamber. A drive shaft is rotatably supported by the front housing member. An end of the drive shaft is exposed from the front housing member and received in the crank chamber. In the crank chamber, a swash plate is supported by the drive shaft such that the inclination angle of the swash plate is changeable. Each of the cylinder bores accommodates a piston and allows the piston to reciprocate. A pair of front and rear shoes are arranged between the swash plate and each of the pistons. Each pair of shoes convert swinging of the swash plate into reciprocation of the associated piston. The compressor includes a displacement control mechanism for adjusting displacement through pressure in the crank chamber.

The displacement control mechanism has a bleed passage, through which the crank chamber communicates with the suction chamber, a supply passage, through which the crank chamber communicates with the discharge chamber, and a displacement control valve. The displacement control valve detects the pressure in the suction chamber to change the opening degree of the supply passage in correspondence with the detected pressure, thus varying the displacement.

The compressor also has a valve chamber, which is formed in the cylinder block to connect the crank chamber and the suction chamber. The valve chamber accommodates a temperature sensitive member, which deforms in correspondence with the temperature in the crank chamber, and a valve body, which is supported by the temperature sensitive member.

The compressor is employed as an air conditioner for a vehicle, in combination with a condenser, an expansion valve, and an evaporator. The compressor can be driven by the engine of the vehicle without employing an electromagnetic clutch. In this case, even when the air conditioner is turned off to stop air conditioning in the passenger compartment, the compressor continuously operates at the minimum displacement as long as the engine operates. In other words, the compressor is maintained in OFF operation. If the compressor continues its operation at displacement other than the minimum displacement, such operation is referred to as ON operation.

In the OFF operation, the inclination angle of the swash angle is minimized, which substantially prevents refrigerant circulation in an external refrigeration circuit outside the compressor. As a result, lubricant oil in circulating refrigerant is maintained in the crank chamber and sheared by components including the swash plate, which is likely to heat the oil. This effect is pronounced particularly when the vehicle is traveling at a high speed. In this state, the temperature sensitive member deforms due to the temperature rise in the crank chamber of the compressor, thus causing the valve body to permit communication between the crank chamber and the suction chamber. This moves the lubricant oil from the crank chamber into the suction chamber to prevent an excessive temperature increase. As a result, the compressor maintains lubricating performance by means of lubricant oil and exhibits improved durability brought about by a shaft sealing device.

However, in the conventional compressor, the valve chamber extends from the front surface of the cylinder block, which faces the crank chamber, parallel to the axis of the drive shaft. It thus becomes difficult for the lubricant oil in the crank chamber to be drawn into the valve chamber via the front surface of the cylinder block. This hampers movement of the lubricant oil from the crank chamber to the suction chamber, thus making it difficult to prevent a temperature rise. To solve this problem, the cross-sectional flow passage area of the valve chamber may be increased. However, this promotes movement of blow-by gas to enter the suction chamber through the valve chamber and causes power loss, which decreases efficiency of the compressor.

Also, the valve chamber extending parallel to the axis of the drive shaft complicates machining and assembly of components, thus increasing the manufacturing costs.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a swash plate type variable displacement compressor capable of preventing a temperature rise in the compressor while minimizing power loss and decreasing the manufacturing costs.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a swash plate type variable displacement compressor is provided that includes a housing, a drive shaft, a swash plate, a piston, a movement conversion mechanism, and a displacement control mechanism. The housing has a cylinder bore, a suction chamber, a discharge chamber, and a crank chamber. The drive shaft is rotatably supported by the housing and exposed in the crank chamber. The swash plate is supported by the drive shaft in the crank chamber such that the inclination angle of the swash plate is changeable. The piston is received in the cylinder bore in a manner reciprocally movable. The movement conversion mechanism is arranged between the swash plate and the piston to convert swinging of the swash plate to reciprocation of the piston. The displacement control mechanism is adapted for adjusting displacement using pressure in the crank chamber. The housing includes a peripheral wall that surrounds the crank chamber in a circumferential direction with respect to the axis of the drive shaft and has an outer surface and an inner surface. The peripheral wall includes a valve chamber recessed radially inward from the outer surface of the peripheral wall, a first oil discharge passage that has an opening in the inner surface of the peripheral wall and allows communication between the crank chamber and the valve chamber, and a second oil discharge passage that allows communication between the valve chamber and the suction chamber. A temperature sensitive member, which deforms in correspondence with the temperature in the crank chamber, is arranged in the valve chamber. A valve body supported by the temperature sensitive member is located in the valve chamber. When the temperature in the crank chamber exceeds a predetermined value to deform the temperature sensitive member and move the valve body, communication between the first oil discharge passage and the second oil discharge passage is permitted through the valve chamber.

Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view showing a compressor according to a first embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view showing a main portion of the compressor of the first embodiment in a state where the temperature in the crank chamber is lower than a predetermined value;

FIG. 3 is an enlarged cross-sectional view showing the main portion of the compressor of the first embodiment in a state where the temperature in the crank chamber is higher than the predetermined value;

FIG. 4 is an enlarged cross-sectional view showing a main portion of the compressor of the first embodiment in a state where a drive shaft rotates at a low speed;

FIG. 5 is an enlarged cross-sectional view showing a main portion of the compressor of the first embodiment in a state where the drive shaft rotates at a high speed; and

FIG. 6 is a lateral cross-sectional view showing a compressor according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Swash plate type variable displacement compressors according to first and second embodiments of the present invention will now be described with reference to the attached drawings.

First Embodiment

As shown in FIG. 1, a swash plate type variable displacement compressor 1 according to the first embodiment is connected to a check valve 2, a condenser 3, an expansion valve 7, an evaporator 9, and a pipe 56 for connecting the aforementioned components together. The compressor 1 thus forms part of an air conditioner for a vehicle. The compressor 1 is a clutchless compressor driven by an engine 6 of the vehicle without employing an electromagnetic clutch.

The compressor 1 includes a housing having a cylinder block 10, a front housing member 12, and a rear housing member 14. The cylinder block 10 has a plurality of cylinder bores 10 a, which are parallel to the axis O of a drive shaft 16 and extend through the cylinder block 10. The left side in FIG. 1 corresponds to the front side of the compressor 1, and the right side of the drawing corresponds to the rear side of the compressor 1.

The rear housing member 14 has a suction chamber 20 and a discharge chamber 22, which communicate with the cylinder bores 10 a through a valve unit 18. Broadly known suction and discharge valve mechanisms are formed in the valve unit 18. The cylinder bores 10 a communicate with the suction chamber 20 through the suction valve mechanism. The cylinder bores 10 a also communicate with the discharge chamber 22 through the discharge valve mechanism. The suction chamber 20 is arranged at the center of the rear housing member 14 and the discharge chamber 22 is formed in an outer peripheral portion of the rear housing member 14. The front housing member 12 and the cylinder block 10 form a crank chamber 24. A shaft hole 12 a and a shaft hole 10 b are formed in the front housing member 12 and the cylinder block 10, respectively. A shaft sealing device 28 is arranged in the shaft hole 12 a. The shaft sealing device 28 is formed of rubber. A plain bearing 30 is mounted in the shaft hole 10 b. A rear chamber 10 c, which communicates with the shaft hole 10 b, is formed at the center of the rear end of the cylinder block 10. The rear chamber 10 c faces the valve unit 18.

The drive shaft 16 is rotatably supported by the front housing member 12 and the cylinder block 10. One end of the drive shaft 16 is exposed from the front housing member 12 and a middle portion of the drive shaft 16 is in the crank chamber 24. A non-illustrated pulley is connected to the drive shaft 16. The drive shaft 16 is driven in a clutchless manner by the engine 6 through a belt wound around the pulley. Each of the cylinder bores 10 a accommodates a piston 32 and allows the piston 32 to reciprocate. Each one of the pistons 32 forms a compression chamber in the associated one of the cylinder bores 10 a.

A lug plate 34, which receives compression reactive force, is fixed to the drive shaft 16 in the crank chamber 24. A thrust bearing 36 and a plain bearing 38 are located between the lug plate 34 and the front housing member 12. A swash plate 40 is mounted around the drive shaft 16 and has a changeable inclination angle with respect to an imaginary plane perpendicular to the drive shaft 16. The lug plate 34 has a hinge portion 34 a, which projects toward the swash plate 40. A hinge portion 40 a is formed in the swash plate 40 and projects toward the lug plate 34. The hinge portions 34 a, 40 a form a link mechanism 42. A pressing spring 44 is arranged between the lug plate 34 and the swash plate 40 to urge the lug plate 34 and the swash plate 40 apart from each other.

A pair of front and rear shoes 46 is mounted between the swash plate 40 and each of the pistons 32. Specifically, the front shoe 46 is arranged between the front surface of the swash plate 40 and the front seating surface of each piston 32 and the rear shoe 46 is located between the rear surface of the swash plate 40 and the rear seating surface of the piston 32. Each of the shoes 46 has a substantially semispherical shape. The shoes 46 form a movement conversion mechanism.

The cylinder block 10 and the valve unit 18 have a bleed passage 11, which has an opening in the front surface of the cylinder block 10 facing the crank chamber 24 and extends parallel to the axis O to allow communication between the crank chamber 24 and the suction chamber 20. The cylinder block 10, the valve unit 18, and the rear housing member 14 have supply passages 52 a, 52 b, through which the crank chamber 24 communicates with the discharge chamber 22.

The rear housing member 14 accommodates a displacement control valve 48. The displacement control valve 48 is connected to the suction chamber 20 through a detection passage 50 and allows communication between the suction chamber 20 and the crank chamber 24 through the supply passages 52 a, 52 b. The displacement control valve 48 changes the opening degrees of the supply passages 52 a, 52 b by detecting the pressure in the suction chamber 20, thus varying displacement of the compressor 1. A known valve body and valve seat (neither is shown) are arranged in the displacement control valve 48. The space between the valve body and the valve seat functions as a restriction.

The front housing member 12 has a peripheral wall 121, which is located in an outer peripheral zone of the crank chamber 24 and surrounds the crank chamber 24 in a circumferential direction about the axis O. A bulging portion 121 a and a bulging portion 14 a, which bulge radially outward, are formed in a portion of the peripheral wall 121 and a portion of the rear housing member 14, respectively. The bulging portion 121 a and the bulging portion 14 a have an attachment leg 121 b and an attachment leg 14 b, respectively, to fix the compressor 1.

With reference to FIGS. 2 and 3, the bulging portion 121 a has a valve chamber 80, which is recessed radially inward from an outer surface 121 c of the bulging portion 121 a with respect to the axis O. The valve chamber 80 includes a large diameter chamber 80 a and a small diameter chamber 80 b. The large diameter chamber 80 a is arranged at the side corresponding to the outer surface 121 c, which is the radially outer side. The small diameter chamber 80 b is formed coaxially and integrally with the large diameter chamber 80 a. The small diameter chamber 80 b is located at the side corresponding to an inner surface 121 d of the peripheral wall 121, which is the radially inner side. The diameter of the small diameter chamber 80 b is smaller than the diameter of the large diameter chamber 80 a.

The inner surface 121 d has a cylindrical surface 121 e, which extends parallel to the axis O. The crank chamber 24 and the small diameter chamber 80 b communicate with each other through a first oil discharge passage 81, which has an opening in the cylindrical surface 121 e and extends perpendicular to the axis O.

The small diameter chamber 80 b communicates with a first hole 82 a, which is formed in the peripheral wall 121 and extends parallel to the axis O. As illustrated in FIG. 1, the first hole 82 a communicates with a second hole 82 b, which is formed in the cylinder block 10 and extends parallel to the axis O. The second hole 82 b communicates with a third hole 82 c extending through the valve unit 18. The third hole 82 c communicates with the suction chamber 20 through a fourth hole 82 d, which is formed in the rear housing member 14. The first, second, third, and fourth holes 82 a, 82 b, 82 c, and 82 d form a second oil discharge passage 82.

With reference to FIGS. 2 and 3, a casing 91 is received in the large diameter chamber 80 a of the valve chamber 80 and fixed using a snap ring 92. An O-ring 93 is arranged in the outer peripheral surface of the casing 91. A valve body chamber 91 a, which is coaxial with the small diameter chamber 80 b, is formed in the casing 91 at the side facing the small diameter chamber 80 b. A bimetal member chamber 91 b is arranged around and formed integrally with the valve body chamber 91 a. The bimetal member chamber 91 b accommodates a bimetal member 94 serving as a temperature sensitive member in a deformable manner. A valve body 95 is received in the small diameter chamber 80 b and the valve body chamber 91 a.

The valve body 95 is configured by a small diameter portion 95 a arranged at the side facing the first oil discharge passage 81 and a large diameter portion 95 b having a diameter greater than the diameter of the small diameter portion 95 a. The bimetal member 94 is held in contact with the step between the small diameter portion 95 a and the large diameter portion 95 b. The small diameter portion 95 a of the valve body 95 has an inner end surface that faces the first oil discharge passage 81, and the inner end surface functions as a valve portion for selectively opening and closing the first oil discharge passage 81. A recess 95 e is formed in the inner end surface of the small diameter portion 95 a. A part in the small diameter chamber 80 b that faces the inner end surface of the small diameter portion 95 a serves as a valve seat.

A spring seat 95 c is formed in the outer end surface of the large diameter portion 95 b in a recessed manner. A compression spring 96 serving as an urging member is arranged between the inner bottom surface of the spring seat 95 c and the bottom surface of the valve body chamber 91 a. The valve body 95 has a communication hole 95 d, through which the small diameter chamber 80 b communicates with the spring seat 95 c. The casing 91, the valve body 95, the bimetal member 94, and the compression spring 96 form a temperature sensitive on-off valve 90.

As illustrated in FIG. 1, the drive shaft 16 has a first hole 62 and a second hole 64, each of which extends in a radial direction. The drive shaft 16 also has a communication hole 66, which extends in the axial direction, or, in other words, coaxially with the axis O, to allow communication between the first hole 62 and the second hole 64. The drive shaft 16 further includes an outlet hole 68, which extends coaxially with the communication hole 66 from the rear end of the second hole 64 communicating with the communication hole 66 to the rear end of the drive shaft 16. The boundary between the communication hole 66 and the outlet hole 68 is an opening degree regulation port 68 a (see FIGS. 4 and 5).

The first hole 62 extends from the axis O to the outer peripheral surface of the drive shaft 16 at a position between the lug plate 34 and the front housing member 12 such that the length of the first hole 62 corresponds to the radius of the drive shaft 16. The front housing member 12 has an oil guide groove 12 b, which extends from the outer peripheral zone of the crank chamber 24 to a position between the front housing member 12 and the lug plate 34, reaching the thrust bearing 36. The front housing member 12 also includes an oil guide hole 12 c, which communicates with the oil guide groove 12 b and reaches the plain bearing 38 and the shaft sealing device 28. The oil guide hole 12 c reaches the shaft sealing device 28 and communicates with the shaft sealing device 28 in the shaft hole 12 a.

The second hole 64 is formed between the lug plate 34 and the swash plate 40 at a position rearward to the first hole 62 and extends through the drive shaft 16. As illustrated in FIGS. 4 and 5, the second hole 64 has a valve seat 64 c, a first radial hole 64 a, and a second radial hole 64 b. The valve seat 64 c is formed in an outer peripheral portion of the drive shaft 16. The first radial hole 64 a extends from the valve seat 64 c and through the drive shaft 16, communicating with the crank chamber 24. The second radial hole 64 b extends from an opposite outer peripheral portion of the drive shaft 16 toward the first radial hole 64 a in a manner extending through the drive shaft 16 and communicates with the crank chamber 24. The diameter of the second radial hole 64 b is substantially equal to the diameter of the first radial hole 64 a. The first radial hole 64 a and the second radial hole 64 b communicate with each other, with a spring seat 64 d formed between the first radial hole 64 a and the second radial hole 64 b.

The valve seat 64 c is formed around the first radial hole 64 a. In the second hole 64, the first radial hole 64 a and the second radial hole 64 b communicate with the outlet hole 68 at the opening degree regulation port 68 a. The first radial hole 64 a has a first opening 64 e, which communicates with the opening degree regulation port 68 a and extends to the crank chamber 24 through the valve seat 64 c. The second radial hole 64 b includes a second opening 64 f, which communicates with the opening degree regulation port 68 a and extends to the crank chamber 24. With reference to FIG. 1, the second opening 64 f is located at the opposite side to the hinge portion 34 a of the lug plate 34 with respect to the axis O of the drive shaft 16.

The second hole 64 receives a centrifugal on-off valve 70. As illustrated in FIGS. 4 and 5, the centrifugal on-off valve 70 faces the first opening 64 e, rather than the axis O of the drive shaft 16. The centrifugal on-off valve 70 is configured by a valve body 72, a mass body 74, a joint bar 76, and a spring 78. The valve body 72 can be seated on the valve seat 64 c. The joint bar 76 joins the valve body 72 and the mass body 74 together such that the valve body 72 is movable. The spring 78 urges the valve body 72 to open the first opening 64 e. The mass body 74 is located closer to the second opening 64 f than the axis O of the drive shaft 16 and capable of changing the opening degree of the opening degree regulation port 68 a. The valve body 72 is received in the first radial hole 64 a. The mass body 74 is accommodated in the second radial hole 64 b. The valve body 72 and the joint bar 76 are both formed of a material lighter than the material of the mass body 74. The spring 78 is arranged between the valve body 72 and the spring seat 64 d.

With reference to FIG. 1, the rear end of the drive shaft 16 projects into the rear chamber 10 c. A tubular spacer 60 is engaged with the outer peripheral surface of the rear end of the drive shaft 16. The spacer 60 makes sliding contact with the valve unit 18 and urges the drive shaft 16 forward. The valve unit 18 has a restriction hole 18 a, which extends through the valve unit 18 and allows communication between the space in the spacer 60 and the suction chamber 20.

The oil guide groove 12 b, the oil guide hole 12 c, the first hole 62, the second hole 64, the communication hole 66, the outlet hole 68, the restriction hole 18 a, and the centrifugal on-off valve 70 form a centrifugal oil discharge valve mechanism. The bleed passage 11, the supply passages 52 a, 52 b, the detection passage 50, and the displacement control valve 48 form a displacement control mechanism.

In the rear housing member 14, the check valve 2 is arranged downstream to the discharge chamber 22. The pipe 56 is connected to an outlet port 54 b, which is downstream to the check valve 2. The pipe 56 extends through the condenser 3, the expansion valve 7, and the evaporator 9 and is connected to the suction chamber 20. The compressor 1, the condenser 3, the expansion valve 7, the evaporator 9, and the pipe 56 form a refrigeration circuit. Circulating refrigerant, which is prepared by mixing lubricant oil with refrigerant, is sealed in the refrigeration circuit.

In the air conditioner for a vehicle, which is configured as described above, the displacement control valve 48 adjusts the pressure in the crank chamber 24 of the compressor 1 based on the pressure in the suction chamber 20, thus changing the angle between the swash plate 40 and an imaginary plane that is perpendicular to the drive shaft 16. This varies the displacement of the compressor 1.

When the compressor 1 is in OFF operation, in which the compressor 1 continues its operation at the minimum displacement, the inclination angle of the swash plate 40 is the minimum. This substantially prevents refrigerant circulation in an external refrigeration circuit outside the compressor 1. Meanwhile, centrifugal force causes splashing of the lubricant oil adhered to components including the drive shaft 16 and the swash plate 40. This will thoroughly lubricate the inner surface 121 d of the peripheral wall 121, which is the outer peripheral zone of the crank chamber 24. The lubricant oil in the crank chamber 24 is then easily introduced into the first oil discharge passage 81, which has an opening in the inner surface 121 d. Accordingly, for example, when the vehicle travels at a high speed and lubricant oil is sheared intensely and heated in the crank chamber 24, the heated lubricant oil is sent through the first oil discharge passage 81 to act on the bimetal member 94 quickly.

Particularly, in the compressor 1, the inner surface 121 d has the cylindrical surface 121 e extending parallel to the axis O of the drive shaft 16 and the first oil discharge passage 81 has the opening in the cylindrical surface 121 e. This further reliably sends lubricant oil from the crank chamber 24 into the first oil discharge passage 81 through centrifugal force.

When the temperature in the small diameter chamber 80 b exceeds a predetermined value, the bimetal member 94 is raised from the valve seat against the urging force produced by the compression spring 96, as illustrated in FIG. 3. The compression spring 96 prevents unstable movement of the valve body 95. In this state, the valve body 95 causes communication between the first oil discharge passage 81 and the second oil discharge passage 82. The crank chamber 24 thus communicates with the suction chamber 20. This rapidly sends lubricant oil from the crank chamber 24 to the suction chamber 20 via the valve chamber 80 and the second oil discharge passage 82, thus preventing a temperature rise.

Particularly, in the compressor 1, if the vehicle runs at a high speed, for example, and the drive shaft 16 rotates at a speed exceeding a predetermined value, intense centrifugal force separates the mass body 74 of the centrifugal on-off valve 70 from the axis of the drive shaft 16 against the urging force of the spring 78, as illustrated in FIG. 5, regardless of the inclination angle of the swash plate 40, or, in other words, regardless of whether the compressor 1 is in OFF operation or ON operation. This causes the valve body 72 to decrease the opening degree of the first opening 64 e. As the rotation speed of the drive shaft 16 increases, the valve body 72 becomes seated on the valve seat 64 c, thus decreasing the opening degree of the second hole 64, which communicates with the opening degree regulation port 68 a. This increases the opening degree of the opening degree regulation port 68 a with respect to the first hole 62 illustrated in FIG. 1. In other words, the centrifugal on-off valve 70 increases the opening degree of the opening degree regulation port 68 a with respect to the first hole 62 and decreases the opening degree of the second hole 64. The outer peripheral zone of the crank chamber 24 is a lubricant-rich zone and lubricant oil is sent from the zone to the first hole 62 through the oil guide groove 12 b and the oil guide hole 12 c. At this stage, the lubricant oil is guided to the first hole 62 via the shaft sealing device 28. As a result, a great amount of lubricant oil is supplied to the shaft sealing device 28, thus improving durability of the rubber used in the shaft sealing device 28.

In this state, the amount of lubricant oil in the circulating refrigerant sent to the refrigeration circuit external to the compressor 1 increases. However, since the pistons 32 reciprocate at a high speed, refrigerating performance is prevented from deteriorating.

As a result, the compressor 1 maintains lubricating performance by means of lubricant oil and exhibits enhanced durability through the shaft sealing device 28 compared to conventional techniques.

If the temperature in the small diameter chamber 80 b drops to a value less than the predetermined value, the bimetal member 94 yields to the urging force of the compression spring 96 and operates to seat the valve body 95 on the valve seat. Also in this case, the compression spring 96 prevents unstable movement of the valve body 95. In this state, the valve body 95 prohibits communication between the first oil discharge passage 81 and the second oil discharge passage 82. The crank chamber 24 is thus prevented from communicating with the suction chamber 20. This blocks movement of lubricant oil from the crank chamber 24 to the suction chamber 20 via the valve chamber 80 and the second oil discharge passage 82.

Particularly, in the compressor 1, the valve body 95 has the recess 95 e, which accommodates foreign matter when the valve body 95 is seated, thus preventing insufficient seating.

In the compressor 1, if the vehicle travels at a low speed, for example, and the drive shaft 16 rotates at a speed lower than the predetermined value, small centrifugal force causes the mass body 74 of the centrifugal on-off valve 70 to yield to the urging force of the spring 78 and approach the axis O of the drive shaft 16, as illustrated in FIG. 4, regardless of whether the compressor 1 is in OFF operation or ON operation. The valve body 72 thus increases the opening degree of the first opening 64 e. As the rotation speed of the drive shaft 16 drops, the mass body 74 contacts the backside of the spring seat 64 d, thus blocking a half area of the opening degree regulation port 68 a. This increases the opening degree of the second hole 64 communicating with the opening degree regulation port 68 a and decreases the opening degree of the opening degree regulation port 68 a with respect to the first hole 62 illustrated in FIG. 1. An inner peripheral zone of the crank chamber 24, which is close to the drive shaft 16, contains a small amount of lubricant oil. Circulating refrigerant thus containing less lubricant oil is sent from the zone to the second hole 64. The second hole 64, which has a greater opening degree, thus introduces the circulating refrigerant with less lubricant oil from the crank chamber 24 to the suction chamber 20 via the outlet hole 68 and the restriction hole 18 a. This decreases the amount of lubricant oil in the circulating refrigerant sent into the refrigeration circuit external to the compressor 1, thus ensuring high refrigerating performance.

At this stage, the amount of lubricant oil increases in the crank chamber 24. However, components including the swash plate 40 simply stir the lubricant oil at a low speed. This substantially prevents a temperature increase in the lubricant oil, thus restricting viscosity decrease in the lubricant oil. As a result, sliding portions are maintained in a desirably lubricated state.

Since the compressor 1 operates in the above-described manner, it is unnecessary to have excessively great cross-sectional flow passage areas for the first oil discharge passage 81, the valve chamber 80, and the second oil discharge passage 82. The bleed passage 11 does not have to have an excessively great cross-sectional flow passage area, either. As a result, blow-by gas is prevented from entering the suction chamber 20 via the first oil discharge passage 81, the valve chamber 80, and the second oil discharge passage 82 or through the bleed passage 11. This decreases power loss in the compressor 1, thus improving efficiency of the compressor 1.

Further, in the compressor 1, the valve chamber 80 is shaped in a manner recessed radially inward from the outer surface 121 c. The first oil discharge passage 81 extends from the valve chamber 80 and has the opening in the inner surface 121 d of the peripheral wall 121. This configuration facilitates machining of the front housing member 12 and mounting of the bimetal member 94 and the valve body 95. As a result, the manufacturing cost is decreased.

Accordingly, the compressor 1 is capable of preventing a temperature rise while minimizing power loss, as well as decreasing the manufacturing costs.

The compressor 1 has the bulging portion 121 a, which is formed in the peripheral wall 121 and extends radially outward. The attachment leg 121 b and the valve chamber 80 are formed in the bulging portion 121 a. Since the valve chamber 80 is inside the bulging portion 121 a, the valve chamber 80 is prevented from interference by peripheral devices of the vehicle. Also, since the bulging portion 121 a, in which the valve chamber 80 is arranged, extends integrally from the attachment leg 121 b, it is unnecessary to form an additional bulging portion exclusively used for the valve chamber 80. The housing is thus prevented from having a complicated outline and increased weight.

Second Embodiment

In the compressor according to the second embodiment of the invention, the front housing member 12, the cylinder block 10, and the rear housing member 14 are fastened together using bolts 13, as illustrated in FIG. 6. The cylinder block 10 has bolt holes 83, through which the corresponding bolts 13 are passed. In the compressor, each of the bolt holes 83 functions as a second oil discharge passage.

The bulging portion 121 a is formed in the peripheral wall 121 of the front housing member 12. A suction joint 122 and the valve chamber 80 are formed in the bulging portion 121 a. The suction joint 122 communicates with the suction chamber 20 in the rear housing member 14 and is connected to the evaporator 9 through a pipe. The other portions of the compressor according to the second embodiment are configured identically with the corresponding portions of the compressor 1 according to the first embodiment.

The compressor of the second embodiment makes it unnecessary to form a second bleed passage particularly and thus further decreases the manufacturing cost. The compressor of the second embodiment has the same advantages as the advantages brought about by the first embodiment.

The first and second embodiments of the present invention have been described. However, the invention is not restricted to the first or second embodiment but may be embodied as modified as needed without departing from the gist of the invention.

For example, in the compressor of the second embodiment, a discharge joint and the valve chamber 80 may be formed in the bulging portion 121 a of the front housing member 12. The discharge joint communicates with the discharge chamber 22 in the rear housing member 14 and is connected to the check valve 2 through a pipe.

In each of the above embodiments, in place of the bimetal member 94, a shape-memory alloy may be used as the temperature sensitive member.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

1. A swash plate type variable displacement compressor, comprising: a housing having a cylinder bore, a suction chamber, a discharge chamber, and a crank chamber; a drive shaft, which is rotatably supported by the housing and exposed in the crank chamber; a swash plate supported by the drive shaft in the crank chamber such that the inclination angle of the swash plate is changeable; a piston received in the cylinder bore in a manner reciprocally movable; a movement conversion mechanism arranged between the swash plate and the piston to convert swinging of the swash plate to reciprocation of the piston; and a displacement control mechanism for adjusting displacement using pressure in the crank chamber, wherein the housing includes a peripheral wall that surrounds the crank chamber in a circumferential direction with respect to the axis of the drive shaft and has an outer surface and an inner surface, the peripheral wall includes a valve chamber recessed radially inward from the outer surface of the peripheral wall, a first oil discharge passage that has an opening in the inner surface of the peripheral wall and allows communication between the crank chamber and the valve chamber, and a second oil discharge passage that allows communication between the valve chamber and the suction chamber, wherein a temperature sensitive member, which deforms in correspondence with the temperature in the crank chamber, is arranged in the valve chamber, and a valve body supported by the temperature sensitive member is located in the valve chamber, and when the temperature in the crank chamber exceeds a predetermined value to deform the temperature sensitive member and move the valve body, communication between the first oil discharge passage and the second oil discharge passage is permitted through the valve chamber.
 2. The compressor according to claim 1, wherein the inner surface has a cylindrical surface extending parallel to the axis, the first oil discharge passage having the opening in the cylindrical surface.
 3. The compressor according to claim 1, wherein the valve body has a surface facing the first oil discharge passage, and a recess is formed in the surface.
 4. The compressor according to claim 1, wherein the second oil discharge passage is a bolt hole, through which a bolt for fastening the housing is passed.
 5. The compressor according to claim 1, further including an urging member arranged in the valve chamber, wherein the urging member urges the valve body in a direction opposite to the direction in which the valve body moves when the temperature in the crank chamber exceeds the predetermined value.
 6. The compressor according to claim 1, wherein a bulging portion that bulges radially outward is formed in the peripheral wall, and the valve chamber is formed in the bulging portion.
 7. The compressor according to claim 1, wherein the displacement control mechanism has a centrifugal oil discharge valve mechanism, which sends lubricant oil from the crank chamber to the suction chamber when the drive shaft rotates at a speed greater than a predetermined speed. 